use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_tool_lint, impl_lint_pass};

mod absurd_extreme_comparisons;

declare_clippy_lint! {
    /// ### What it does
    /// Checks for comparisons where one side of the relation is
    /// either the minimum or maximum value for its type and warns if it involves a
    /// case that is always true or always false. Only integer and boolean types are
    /// checked.
    ///
    /// ### Why is this bad?
    /// An expression like `min <= x` may misleadingly imply
    /// that it is possible for `x` to be less than the minimum. Expressions like
    /// `max < x` are probably mistakes.
    ///
    /// ### Known problems
    /// For `usize` the size of the current compile target will
    /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
    /// a comparison to detect target pointer width will trigger this lint. One can
    /// use `mem::sizeof` and compare its value or conditional compilation
    /// attributes
    /// like `#[cfg(target_pointer_width = "64")] ..` instead.
    ///
    /// ### Example
    /// ```rust
    /// let vec: Vec<isize> = Vec::new();
    /// if vec.len() <= 0 {}
    /// if 100 > i32::MAX {}
    /// ```
    #[clippy::version = "pre 1.29.0"]
    pub ABSURD_EXTREME_COMPARISONS,
    correctness,
    "a comparison with a maximum or minimum value that is always true or false"
}

pub struct Operators;
impl_lint_pass!(Operators => [
    ABSURD_EXTREME_COMPARISONS,
]);
impl<'tcx> LateLintPass<'tcx> for Operators {
    fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
        if let ExprKind::Binary(op, lhs, rhs) = e.kind {
            if !e.span.from_expansion() {
                absurd_extreme_comparisons::check(cx, e, op.node, lhs, rhs);
            }
        }
    }
}